JPH04173803A - Production of vinyl chloride-based polymer - Google Patents

Abstract

PURPOSE:To obtain the title polymer having good absorption of plasticizer and fish eye amount by subjecting vinyl chloride monomer, etc., to suspension polymerization in an aqueous medium using PVA having a specific saponification degree and hydroxypropylmethyl cellulose having specific substitution degree as dispersants. CONSTITUTION:A vinyl chloride monomer or mixture of vinyl-based monomers consisting essentially of the vinyl chloride monomer is subjected to suspension polymerization in an aqueous medium in the presence of a oil-soluble polymerization initiator using (A) a vinyl alcohol-based polymer containing 3-15mol% recurring units expressed by the formula (R is pyrrolidone group, caprolactam group, oxazoline group or 5-methyloxazoline group) and having 70-85mol% saponification degree and 500-2000 polymerization degree, (B) hydroxypropylmethyl cellulose having 26-30wt.% methoxy substitution degree and 4-15wt.% hydroxypropoxy substitution degree and 5-4000cPs viscosity of 2wt.% aqueous solution thereof at 20 deg.C as dispersion stabilizers at a wt. ratio of the component A/B of 20/80 to 80/20 and in total amount of the dispersion stabilizers of 0.02-0.3 pts.wt. based on 100 pts.wt. said monomer to provide the objective polymer.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to a method for producing a vinyl chloride polymer, and in particular to a method for producing a vinyl chloride polymer, which has a wide range of applications due to its excellent plasticizer absorption and fisheye content. This relates to a manufacturing method.

(Prior Art) Polyvinyl chloride (hereinafter referred to as PVC) is a useful resin with excellent physical properties and is widely used in various fields ranging from hard to soft.

Among these, since various plasticizers are used in the soft field, one of the important properties required of PVC is excellent plasticizer absorption. To improve this, the PvC particles must be made more porous.

Many PVC manufacturing methods have been proposed for this purpose. For example, in the common axis of JP-A-52-115890, the saponification degree is 37 to 70 mol% and the polymerization degree is 160 to 50 mol%.
A method for producing porous PVC is described, which involves suspension polymerization of vinyl chloride in the presence of partially saponified polyvinyl alcohol of 0.0%. In addition, in JP-A-57-14607 and JP-A-60-229907, polymerization is started using a surfactant or polyvinyl alcohol with a low degree of saponification as a dispersant, and when a predetermined polymerization rate is reached, water-soluble A method of obtaining porous PVC by adding a dispersing agent is disclosed.

According to these manufacturing methods, it is possible to obtain PVC that is porous to some extent and has excellent plasticizer absorption properties, but on the other hand, scale tends to adhere to the interior of the polymerization can.

We also increased the ratio of vinyl chloride monomer in the preparation.

If the polymerization time is shortened, the resulting polymer becomes coarse or lumpy, resulting in a decrease in quality, and is not sufficient in terms of production efficiency.

This is thought to be because surfactants and polyvinyl alcohol with a low degree of saponification are used from the initial stage of polymerization, which eliminates the skin layer on the surface of the polymer particles and makes the suspension system unstable.

(Problems to be Solved by the Invention) Therefore, an object of the present invention is to provide a method for producing a vinyl chloride polymer with high productivity, which has excellent plasticizer absorption and fisheye content, and which has a wide range of applications. It is something.

(Means for Solving the Problems) As a result of intensive research, the present inventors have found that vinyl chloride monomers or a mixture of vinyl monomers mainly composed of vinyl chloride are used in an aqueous polymerization system in the presence of an oil-soluble polymerization initiator. When carrying out suspension polymerization in a medium, A as a dispersion stabilizer, general formula +CH2-CH-
)- (in the formula, R is a pyrrolidone group, a caprolactam group, an oxazoline group or a 5-methyloxazoline group) containing 3 to 15 mol% of repeating units, and having a saponification degree of 70 to 85 mol%. A vinyl alcohol polymer with a degree of polymerization of 500 to 2,000, B, and a degree of methoxy substitution of 2
6-30% by weight, degree of hydroxypropoxy substitution 4-1
5% by weight of hydroxypropyl methylcellulose, whose 2% by weight aqueous solution has a viscosity of 5 to 4,000 cps at 20°C.

When the weight ratio of A/B is 20/80 to 80/20 and the total amount is 0.02 to 0.3 parts by weight per 100 parts by weight of the vinyl chloride monomer or mixture thereof, the above problem can be solved. The present invention was achieved by discovering that the problem can be solved.

The present invention will be explained in detail below.

In the method for producing a vinyl chloride polymer of the present invention, in particular, the repeating unit represented by the above general formula is contained as a dispersion stabilizer in an amount of 3 to 15 mol%, and the degree of saponification is 70 to 85 mol%.
A vinyl alcohol polymer A having a degree of polymerization of 500 to 2,000, a degree of methoxy substitution of 26 to 30% by weight, and a degree of hydroxypropoxy substitution of 4 to 15% by weight;
The viscosity of the weight% aqueous solution at 20°C is 5 to 4.0 OOc.
Two types are used: hydroxypropyl methylcellulose B, which is ps.

When the dispersion stabilizer A has a repeating unit represented by the above general formula of more than 15 mol%, a degree of saponification of less than 70 mol%, or a degree of polymerization of less than 500, the suspension system is The resulting polymer becomes unstable and becomes coarse grained, and conversely, the repeating unit represented by the above general formula is lower than 3 mol%, the degree of saponification exceeds 85 mol%, or the degree of polymerization is 2. ,000, the resulting polymer will have poor plasticizer absorbency and fisheye content.

Dispersion stabilizer B has a degree of methoxy substitution lower than 26% by weight, a degree of hydroxypropoxy substitution lower than 4% by weight, or a viscosity of a 2% aqueous solution at 20°C of 4.
If it is higher than 0OOcps, the plasticizer absorption will decrease, and conversely, the degree of methoxy substitution will be higher than 30% by weight, and the degree of hydroxypropoxy substitution will be higher than 15% by weight. Alternatively, if the viscosity of the 2% by weight aqueous solution at 20° C. is lower than 5 cps, the particle size distribution of the resulting polymer particles will be wide, impairing processability.

The amount of dispersion stabilizers A and B to be charged can be adjusted over a wide range depending on the particle size of the target vinyl chloride polymer, but generally, the charge ratio of both dispersion stabilizers A and B is A.
/B weight ratio of 20/80 to 80/20, preferably 30/70 to 70/30, and the total amount of each is the vinyl chloride monomer or a vinyl monomer mainly composed of vinyl chloride. 0.02 to 0 per 100 parts by weight of the mixture of
．． It is used in a proportion of 3 parts by weight.

If the weight ratio of A/B is less than 20/80, the porosity of the resulting polymer will decrease, and if it exceeds 80/20, the particle size distribution will become wide, which is not preferable.

In the method for producing a vinyl chloride polymer of the present invention, in addition to these dispersion stabilizers, partially saponified polyvinyl alcohol C having a degree of saponification of 20 to 55 mol% and a degree of polymerization of 200 to 600 is added to the above monomers. Or, when used at a ratio of 0.004 to 0.15 parts by weight per 100 parts by weight of the mixture, the porosity of the resulting polymer will be significantly increased, the plasticizer absorption will be improved, gelation will be faster, and the time will be shorter. The quality of the product can be further improved, such as by reducing fish eyes.

However, if the degree of saponification of this dispersant C is lower than 20 mol% or the degree of polymerization is lower than 200, the obtained polymer may become coarse particles or scale may adhere to the inside of the can, and the degree of saponification may be lower than 200. If the amount is higher than 55 mol% or the degree of polymerization exceeds 600, the plasticizer absorbability will decrease. Further, if the amount added exceeds 0.15 parts by weight per 100 parts by weight of the above monomer or mixture thereof, it is not preferable because one polymer becomes coarse grained.

The dispersion stabilizer used in the present invention further has a degree of saponification of 75 to 99 mol% and a degree of polymerization of 1 to 500 to 2.
, 700 partially saponified polyvinyl alcohol can also be used in combination.

To add each of the above dispersion stabilizers to the polymerization system, directly add methanol or methyl acetate.

Any method may be used, such as addition using a solvent such as ethyl acetate or a mixed solvent such as water/methanol, or addition as an aqueous emulsion. In addition, the above-mentioned dispersion stabilizers A and B, as well as the dispersion stabilizers C and D used in combination as necessary, may be used alone or in combination.
The above can be added simultaneously, individually or in a mixture.

In the method for producing a vinyl chloride polymer of the present invention, monomers that are preferably used include vinyl chloride monomers, as well as mixtures of vinyl monomers that are mainly composed of vinyl chloride and copolymerizable with vinyl chloride monomers. (Usually vinyl chloride is 50% by weight or more), and comonomers copolymerized with vinyl chloride include vinyl esters such as vinyl acetate and vinyl propionate; acrylic esters such as methyl acrylate and ethyl acrylate; Examples include methacrylic acid ester; olefins such as ethylene and propylene; maleic anhydride; acrylonitrile: styrene; and vinylidene chloride.

The oil-soluble polymerization initiator used in the present invention may be any one commonly used in the past, such as t-
Butyl peroxy neodecanoate, t-butyl peroxy pivalate, t-hexyl peroxy pivalate,
Perester compounds such as α-cumyl peroxyneodecanoate, hexylneohexanoate, 2,4.4-)-tumethylpentyl-2-peroxy-2-neodecanoate; diisopropyl peroxydicarbonate, Percarbonate compounds such as di-2-ethylhexyl peroxydicarbonate, di-2-ethoxyethyl peroxydicarbonate, dimethoxyisopropyl peroxydicarbonate; decanoyl peroxide, lauroyl peroxide, benzoyl peroxide, cumene hydroba-oxide, Cyclohexanone peroxide, 2,4-dichlorobenzoyl peroxide,
Peroxide compounds such as p-menthane hydroperoxide, 3,5.5-trimethylhexanoyl peroxide, isobutyryl peroxide, acetylcyclohexylsulfonyl peroxide; α, α′-azobisisobutyronitrile, α, α′ Examples include azo compounds such as -azobis(2,4-dimethylvaleronitrile) and α,α′-azobis(4-methoxy-2,4-dimethylvaleronitrile), which may be used alone or in combination of two or more. can be used.

Furthermore, if necessary, this polymerization system includes polymerization regulators, chain transfer agents, etc., which are used as appropriate for the polymerization of vinyl chloride monomers.
It is also optional to add pH adjusters, gelling improvers, antistatic agents, scale inhibitors, and the like.

When producing the vinyl chloride polymer of the present invention, for example, the amount of aqueous medium used per monomer charged, the amount of the polymerization initiator and vinyl chloride monomer, and in some cases, the amount of other comonomers used, and their preparation. The method, polymerization temperature, etc. may be carried out under conventionally known conditions.

(Examples) Hereinafter, specific aspects of the present invention will be explained using Examples and Comparative Examples, but the present invention is not limited thereto.

Examples 1 to 7 and Comparative Examples 1 to 6 In a stainless steel polymerization vessel with an internal volume of 100Q, 60% of pure water, dispersion stabilizers A and B of the type and amount shown in Table 1, and G2 as a polymerization initiator were added. - After charging 22.5 g of ethylhexyl peroxydicarbonate, the internal pressure of the polymerization vessel was 6.
The air was degassed to 0 mnHg. Thereafter, 30 kg of vinyl chloride monomer was charged while stirring the inside of the vessel, and polymerization was started at 57°C while increasing the temperature.

The reaction was stopped when the internal pressure of the polymerization vessel decreased to 6.0 kg/adG, and unreacted monomers were recovered and dehydrated and dried to obtain a vinyl chloride polymer.

Regarding the obtained polymer, bulk specific gravity according to JIS K-6721 and particle size (mesh) according to JIS Z-8801
The distribution, as well as the amount of plasticizer absorption and amount of fish eyes, were measured using the methods described below, and the results are also listed in Table 1.

In addition, the abbreviation symbol in R of the repeating unit shown in the above-mentioned - clothing amount of dispersion stabilizer A in the table means the following.

Further, the abbreviations in the types of dispersion stabilizer B have the following meanings.

Abbreviation Degree of methoxy substitution Degree of substitution of hydropropoquine Viscosity book (wt%) (wt%) (cps
) i 28
6 50ii 28
6 400in
29 10
1.500 (viscosity of 2% by weight aqueous solution at 20°C) Plasticizer absorption: Fill the bottom of an aluminum alloy container with an inner diameter of 25 mm and a depth of 85 mm with glass fiber, and add the sample vinyl chloride polymer to it. Take 10g and add it. DOP for this
Add 15 cc and leave for 30 minutes to allow DOP to fully penetrate into the polymer. Then, with an acceleration of 1500G, the excessive D
The OP is centrifuged and the amount (% by weight) of DOP absorbed by the polymer is determined per 100 parts by weight of the polymer.

・Amount of fish eyes: Sample vinyl chloride polymer 100 parts by weight, tribasic lead sulfate 1 part by weight, lead stearate 1.5 parts by weight, titanium dioxide 0.2 parts by weight, carbon black 0.1 parts by weight, and 25g of a compound mixed with 50 parts by weight of DOP,
The mixture was kneaded with a roll at 145° C. for 3 minutes, separated into a sheet with a thickness of 0.2 m+a, and the number of transparent particles in 100 cm” of this sheet was shown.

Further, the above formulation was kneaded for 5 minutes with a roll at 145°C, and the number of transparent particles was measured in the same manner.

Examples 8 to 14 and Comparative Examples 7 to 12 As dispersion stabilizers, dispersion stabilizers A, C, and D in the types and amounts shown in Table 2 and dispersion stabilizer B (type i) in the amounts shown in the same table were used.
A vinyl chloride polymer was obtained in the same manner as in the previous example except that

Regarding this, bulk specific gravity, particle size distribution, plasticizer absorption amount, fish eye amount, and plasticizer absorption time were measured in the same manner as in the previous example, and the results are also listed in Table 2.

In addition, the abbreviation for R of the repeating unit indicated by the above-mentioned -clothing cost of dispersion stabilizer A in the table is also the same as in the previous example.

・Plasticizer absorption time 400g of polymer powder was placed in a niblastograph (planetary mixer) and preheated to 80°C for 4 minutes while stirring at 60rpm, then 200g of DOP was added to this,
The time from the time of addition to the time when the torque decreased was defined as the plasticizer absorption time.

(Effects of the Invention) According to the method of the present invention, it is possible to obtain a vinyl chloride polymer of extremely high quality and a wide range of applications, which is excellent in plasticizer absorption and fisheye content.

Claims (1)

[Claims] 1. Vinyl chloride monomer or a mixture of vinyl monomers mainly composed of vinyl chloride, in the presence of an oil-soluble polymerization initiator,
When carrying out suspension polymerization in an aqueous medium, there are A, general formulas, mathematical formulas, chemical formulas, tables, etc. as dispersion stabilizers for suspension polymerization in aqueous media. A vinyl alcohol polymer containing 3 to 15 mol% of repeating units represented by ), a saponification degree of 70 to 85 mol%, and a polymerization degree of 500 to 2,000, B, a methoxy substitution degree 2
6-30% by weight, degree of hydroxypropoxy substitution 4-1
Hydroxypropyl methylcellulose having a concentration of 5% by weight and a 2% by weight aqueous solution having a viscosity of 5 to 4,000 cps at 20°C, with an A/B weight ratio of 20/80 to 80/20 and a total amount of A method for producing a vinyl chloride polymer, characterized in that the vinyl chloride monomer or a mixture thereof is used in an amount of 0.02 to 0.3 parts by weight per 100 parts by weight of a vinyl chloride monomer or a mixture thereof. 2. The dispersion stabilizer has C, a degree of saponification of 20 to 55 mol% and a degree of polymerization of 200 to 6.
2. The method for producing a vinyl chloride polymer according to claim 1, wherein 0.004 to 0.15 parts by weight of the partially saponified polyvinyl alcohol No. 00 is used per 100 parts by weight of the vinyl chloride monomer or mixture thereof. 3. The dispersion stabilizer has D. a degree of saponification of 75 to 99 mol% and a degree of polymerization of 1,500.
3. The method for producing a vinyl chloride polymer according to claim 1 or 2, wherein partially saponified polyvinyl alcohol having a molecular weight of 2,700 to 2,700 is used in combination.